02370nas a2200169   4500008004100000245015600041210006900197260000800266300001200274490000700286520169900293100001801992700001802010700001802028700002302046856013102069       2017                        eng d00aEffect of viscoelastic relaxation modes on stability of extrusion film casting process modeled using multi-mode Phan-Thien-Tanner constitutive equation0 aEffect of viscoelastic relaxation modes on stability of extrusio  cJUL  a487-5000 v473 aExtrusion film casting (EFC) is a commercially important process that is used to produce a significant quantity of polymer films, sheets and coatings for both industrial and household applications. Recently, we have demonstrated the influence of polymer chain architecture on the extent of necking under isothermal as well as non-isothermal film casting operation for commercially relevant polyolefin based materials [1-4]. In the present research, we focus on another instability that frequently occurs in high-speed EFC process called as draw resonance. Draw resonance manifests itself as an instability that causes periodic fluctuations in both the width as well as thickness of the extruded molten film above a critical draw ratio (DR). In this work, we have carried out a linear stability analysis of the isothermal EFC process using a multi-mode Phan-Thien-Tanner (PTT) constitutive equation to determine the onset of draw resonance. We show that as the number of relaxation modes is increased there is a dramatic change in the stability regions. In particular, there is a marked variation in the stability regions obtained by Simulating the multi-mode model and those obtained by taking averaged relaxation time of the modes. Additionally, as the number of faster-relaxing modes in a multi-mode spectrum is progressively increased, the process becomes increasingly stable as the level of elasticity in the melt decreases. Finally, the addition of a long relaxation mode in a multi-mode spectrum is akin to adding a long chain branch to a linear polymer that leads to a reduction in film necking and in many cases to enhanced process stability. (C) 2017 Elsevier Inc. All rights reserved.1 aDhadwal, Renu1 aBanik, Sourya1 aDoshi, Pankaj1 aPol, Harshawardhan  uhttps://library.ncl.res.in/content/effect-viscoelastic-relaxation-modes-stability-extrusion-film-casting-process-modeled-using02520nas a2200265   4500008004100000022001400041245014300055210006900198260000800267300001200275490000700287520162200294653001901916653001901935653001901954653001501973653001801988653001402006100002102020700002202041700002902063700002302092700001802115856012102133       2018                        eng d  a0035-451100aNon-isothermal analysis of extrusion film casting using multi-mode Phan-Thien Tanner constitutive equation and comparison with experiments0 aNonisothermal analysis of extrusion film casting using multimode  cJUL  a493-5030 v573 a<p>Extrusion film casting (EFC) is an industrially important process which produces thousands of tons of polymer films, sheets, and coating used for various industrial as well as household applications. In this paper, we focus on an instability which occurs during certain polymer processing operations operating under predominantly elongational flow, such as extrusion film casting and fiber spinning. This instability, called the draw resonance, occurs in the form of sustained periodic fluctuations in the film dimensions. It appears when the process goes beyond the critical line speed of the EFC process. In this work, a conventional linear stability analysis is carried out for nonisothermal EFC process to determine the onset of the draw resonance. The polymer rheology is modeled by the Phan-Thien Tanner (PTT) multi-mode constitutive equation. For the implementation, a conventional shooting method approach is used. Extrusion film casting experiments were also carried out using a conventional linear low-density polyethylene (LLDPE) by varying process parameters such as draw ratio and aspect ratio, to observe the effect on the stability of the process. Linear stability analysis results under non-isothermal conditions are compared and validated with existing results from literature and with our own experimental data. This work displays the effect of multiple relaxation modes as well as the temperature influence on the stability of EFC process. Finally, results also indicate that the temperature highly affects the stability of the EFC process and cannot be ignored from modeling of EFC process.</p>10aDeborah number10aDraw resonance10aFilm extrusion10aMulti-mode10aNonisothermal10astability1 aChougale, Sanket1 aRokade, Dhammaraj1 aBhattacharjee, Tanushree1 aPol, Harshawardhan1 aDhadwal, Renu  uhttps://library.ncl.res.in/content/non-isothermal-analysis-extrusion-film-casting-using-multi-mode-phan-thien-tanner02609nas a2200337   4500008004100000022001400041245017500055210006900230260000800299300002100307490000700328520146600335653001901801653003301820653001401853653000901867653003001876653001301906653001901919653001701938653001301955653001401968100002201982700002102004700002002025700002902045700002502074700002302099700001802122856013102140       2021                        eng d  a8756-087900aControlling draw resonance during extrusion film casting of nanoclay filled linear low-density polyethylene: an experimental study and numerical linear stability analysis0 aControlling draw resonance during extrusion film casting of nano  cJUL  a87560879209784430 v373 a<p>Commercially important extrusion film casting (EFC) processes for manufacturing plastic films or sheets are hampered by several instabilities that severely limits their productivity. In this research we focussed on one important instability: the draw resonance that occurs during the EFC process mainly under extensional flow conditions. Draw resonance is the sustained periodic oscillations in the film dimensions, notably film width and thickness, when the process operates beyond a critical draw ratio (CDR). In this research our goal was to reduce this draw resonance instability by incorporating well dispersed nanoclay fillers in a base polymeric resin (such as a linear low density polyethylene - LLDPE) to determine how these nanocomposite (NC) formulations can prevent or reduce the draw resonance defect. EFC experiments were conducted on the base resin and on the NC formulations under non-isothermal conditions to determine the onset of the draw resonance experimentally. Conventional linear stability analysis was performed to determine the onset of the draw resonance defect numerically. Numerical predictions for the onset of draw resonance were in qualitative agreement with our experimental data. Our results showed that incorporating appropriate nanoclay concentrations in a base polymeric resin indeed enhanced the EFC process stability for those polymer formulations and thus can have important economic implications for processors.</p>
10aDraw resonance10aextensional strain hardening10aExtrusion10aFilm10ahydrodynamic interactions10aNanoclay10aNanocomposites10aPolyethylene10aRheology10astability1 aRokade, Dhammaraj1 aChougale, Sanket1 aPatil, Prashant1 aBhattacharjee, Tanushree1 aGawande, Dnyaneshwar1 aPol, Harshawardhan1 aDhadwal, Renu  uhttps://library.ncl.res.in/content/controlling-draw-resonance-during-extrusion-film-casting-nanoclay-filled-linear-low-density